Abstract:
The atoms in conventional (i.e. alkai) atomic Bose-Einstein
condensates interact via
short-range s-wave interactions which decay as 1/r
6
(van der Waals
interactions).
However, recently a BEC of chromium atoms was made by T. Pfau's group
in Stuttgart [PRL
94, 160401 (2005)]. Chromium has an anomalously large magnetic dipole
moment and
consequently a chromium BEC has large dipole-dipole interactions.
There are also many
efforts going on worldwide to make ultracold polar molecules which
have potentially huge
dipole moments. In this talk I will introduce the theory of trapped
dipolar condensates
and compare it to the results of experiments conducted so far. We
shall see how the
long-range and anisotropic form of the dipole-dipole interaction leads
to new mesoscopic
effects which depend on the shape of the condensate surface. These include
magnetotstriction and an instability towards the formation of a
density wave. Finally, I
will dicuss the role of the sign of the interactions in controlling
the properties of
these novel superfluids under rotation.